machine/usb/hid/joystick: handle case where we cannot find the correct HID descriptor

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/machine/usb.go

@@ -302,7 +302,12 @@ func EnableMIDI(txHandler func(), rxHandler func([]byte), setupHandler func(usb.
 
 // EnableJoystick enables HID. This function must be executed from the init().
 func EnableJoystick(txHandler func(), rxHandler func([]byte), setupHandler func(usb.Setup) bool, hidDesc []byte) {
-	class := descriptor.FindClassHIDType(descriptor.CDCJoystick.Configuration, descriptor.ClassHIDJoystick.Bytes())
+	class, err := descriptor.FindClassHIDType(descriptor.CDCJoystick.Configuration, descriptor.ClassHIDJoystick.Bytes())
+	if err != nil {
+		// TODO: some way to notify about error
+		return
+	}
+
 	class.ClassLength(uint16(len(hidDesc)))
 	descriptor.CDCJoystick.HID[2] = hidDesc
 

src/machine/usb/descriptor/hid.go

@@ -3,6 +3,7 @@ package descriptor
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 )
 
 var configurationCDCHID = [configurationTypeLen]byte{
@@ -76,10 +77,22 @@ func (d ClassHIDType) ClassLength(v uint16) {
 	binary.LittleEndian.PutUint16(d.data[7:9], v)
 }
 
-func FindClassHIDType(data, section []byte) ClassHIDType {
+var errNoClassHIDFound = errors.New("no classHID found")
-	idx := bytes.Index(data, section)
 
-	return ClassHIDType{data: data[idx : idx+ClassHIDTypeLen]}
+// FindClassHIDType tries to find the ClassHID class in the descriptor.
+func FindClassHIDType(des, class []byte) (ClassHIDType, error) {
+	if len(des) < ClassHIDTypeLen || len(class) == 0 {
+		return ClassHIDType{}, errNoClassHIDFound
+	}
+
+	// search only for ClassHIDType without the ClassLength,
+	// in case it has already been set.
+	idx := bytes.Index(des, class[:ClassHIDTypeLen-2])
+	if idx == -1 {
+		return ClassHIDType{}, errNoClassHIDFound
+	}
+
+	return ClassHIDType{data: des[idx : idx+ClassHIDTypeLen]}, nil
 }
 
 var classHID = [ClassHIDTypeLen]byte{

src/machine/usb/hid/joystick/joystick.go

@@ -30,7 +30,7 @@ func UseSettings(def Definitions, rxHandlerFunc func(b []byte), setupFunc func(s
 		State: def.NewState(),
 	}
 	if setupFunc == nil {
-		setupFunc = js.setupFunc
+		setupFunc = hid.DefaultSetupHandler
 	}
 	machine.EnableJoystick(js.handler, rxHandlerFunc, setupFunc, hidDesc)
 	Joystick = js